Abstract
The oxidizing reaction accompanied with decomposition of manganese-magnesium ferrite containing a small amount of copper (Cu 0·08 6 Mg 0·21 4 Mn 0·98 6 Fe 1·71 4 O 4) was studied by quantitatively analysing the measured values of saturation magnetization, crystal lattice constant and ferrimagnetic Curie temperature. The samples were oxidized at various temperatures between 650° and 900°C for some hundreds of minutes in air, and the existing phases were identified by X-ray diffraction. It was recognized that, in the course of the oxidation reaction, the ferrite decomposes into spinel type ferrite and “non-magnetic” α-Fe 2O 3 and Mn 2O 3,and Mn 2O 3, and that decomposition decreases the saturation magnetization, crystal lattice constant and ferrimagnetic Curie temperature. From the obtained results it is concluded that the oxidizing reaction proceeds as follows: Cu 2+ 0·08 6 Mg 2+ 0·021 0 Mn 2+ 0·70 0 Mn 3+ 0·28 6 Fe 3+ 1·71 4 O 4 + δ 2 O 2 ⇌ 3(1 − x)δ Mn 2 O 3 + 1 f Cu 2+ 0·08 6f Mg 2+ 0·21 4f Mn 2+ (0·70 6 − 2δ)f Mn 3+ (0·28 6 − 4δ + 6xδ)f Fe 3+ (1·71 4 − 6xδ)f O 4, where f = 1 1−2δ , and x = 0· − 0·8.
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